WORK OF CARROLL. 



The first part of this work is a continuation of the investigation of Jones 

 and Lindsay. 



EXPERIMENTAL. 

 APPARATUS. 



The Kohlrausch method of measuring conductivity was used throughout 

 this investigation. The bridge-wire was of "manganin." The resistance 

 coils were carefully calibrated. The conductivity cells were of the form used 

 by Jones and Lindsay. The constants of these were determined by means of 

 N/50 and N/500 solutions of potassium chloride. Cells used to determine 

 conductivities of the solvent and of highly diluted solutions were treated in 

 the manner recommended by Whetham. 2 The electrodes were first coated 

 with platinum black in the usual manner, and were afterwards heated to a 

 high temperature in the flame of a blast-lamp. It was found, as Whetham 

 states, that the usual coating of platinum black, in spite of careful and long- 

 continued washing, retains traces of salt that subsequently pass slowly into 

 solution. The oxidizing action of the platinum black is also avoided by this 

 treatment. For the purposes mentioned, electrodes of this kind can not 

 be too highly recommended. The tone-minimum in the telephone is fully 

 as good as with the ordinary type of electrode. 



The 25 thermostat was of the usual (Ostwald) form, and the stirrer was 

 driven by a small hot-air motor. The zero-bath was of the type used by Jones 

 and Lindsay, consisting of an outer and an inner vessel. The inner vessel 

 and the annular space between the two were filled with finely crushed ice. 

 The outer portion of ice was moistened with a small quantity of distilled 

 water, and to the ice in the inner vessel about an equal weight of water was 

 added. By the foregoing means the temperature of a cell immersed in the 

 ice and water of the inner vessel could be kept for any desired period at 

 0.02 to 0.05 C. 



The measuring flasks, pipettes, and burettes were carefully calibrated. 



SOLVENTS. 



The water used was purified in the following manner: Ordinary distilled 

 water, after addition of potassium dichromate and sulphuric acid, was re- 

 distilled. The distillate was again distilled from chromic acid into, and then 

 out of, a solution of barium hydroxide. When the conductivity of the water 

 thus obtained was greater than 2 x 10~ 6 , the above process was repeated. In 

 many cases the conductivity was much less than this value. 



1 Amer. Chem. Journ., 28, 329 (1902). 



2 Phil. Trans., 94 (A), 321 (1900). Ztschr. phys. Chem., 33, 346 (1900). 



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